Cross country pipelines are usually coated with a corrosion-resistant substance. To protect the coating from damage when the ditch is back filled with excavated material, which may contain large rocks, the pipeline is first covered with fine particles of dirt to serve as a protective padding around the pipeline.
U.S. Pat. Nos. 2,857,691, 3,701,422, 4,633,602, 4,861,461 and 4,948,299 relate to apparatus that is moved with or by a vehicle along the side of the ditch for collecting and separating a windrow of excavated material into fine material and coarse material and conveying the fines into the ditch to cover the pipeline and returning the coarse material to the windrow on the ground.
The most pertinent of these patents is U.S. Pat. No. 2,857,691, which issued Oct. 28, 1958 to Donald Michael Curran, and is entitled "Pipeline Ditch Filling and Pipe Padding Machine". This patent discloses the use of a rotating head to separate the excavated material into fine material and coarse material and a conveyor to carry the fines to the ditch. The head and an auger extend laterally from a tractor on one side of the ditch to the windrow of excavated material on the other side of the ditch. The conveyor and the drum are supported in the vertical plane by a flexible cable attached to a boom on the tractor. Therefore, Curran's rotating head cannot be held in a fixed horizontal position. As a result it will remove continuously varying amounts of excavated material requiring the operator to constantly vary the speed and direction of the tractor and the amount of the total weight of the head and the conveyor that is allowed to force the head against the excavated material.
Therefore, it is an object of this invention to provide a method and apparatus for padding a pipeline that includes a rotating drum for separating the fine and coarse particles of the previously excavated material that is mounted on the front of a tractor and is held against vertical movement as the rotating drum is forced through the excavated material at a selected depth to produce a continuous stream of fines for padding the pipeline.
It is a further object of this invention to provide an apparatus for padding a pipeline from either side of the apparatus.
It is a further object of this invention to provide a pipeline padding apparatus that includes a frame for attaching to the front end of a tractor for movement through a windrow of excavated material along the side of the ditch as the tractor moves over the windrow of material, a hollow drum rotatably mounted on the frame having spaced rods for separating fine material from coarse material, means rotatable with the head for lifting a portion of the excavated material upwardly with the drum as the drum rotates causing the material to fall against the rods so the fine material falls between the rods into the drum and the coarse material is carried on the rods and deposited behind the drum back onto the remaining windrow of excavated material extending along the side of the ditch under the moving tractor, and a conveyor that extends through the drum and the sides of the frame to receive the fines and deposit them onto the pipeline in the ditch.